The present invention relates to a novel class of boride-based refractory, abrasive materials or, more particularly, to a class of refractory and abrasive materials based on certain metal diborides as sintered with high density and high mechanical strengths even at elevated temperatures.
With their extremely high melting points and hardness as well as excellent mechanical strengths at elevated temperatures, metal diborides such as titanium diboride are the most promising materials for construction of rockets, cutting tools, parts of thermal engines and the like. When metal diborides are to be sintered for use in these applications, however, difficulties are encountered because the sintering temperature is extremely high and the sintered bodies obtained are poor in the bending strength and relatively brittle regardless of whether the metal diborides are used either singly or as a combination of two or more.
The inventors conducted extensive investigations to solve the above problems in the sintered bodies of metal diborides and discovered that titanium diboride could give excellent sintered bodies when admixed with an alloy of nickel and phosphorus (see, for example, Japanese Patent Publication No. 51-23625).
These titanium diboride-based sintered bodies are developed by the inventors possess a bending strength reaching 100 to 150 kg/mm.sup.2 but, needless to say, even higher bending strengths are sometimes required in the practical use of these kinds of refractory materials. In addition, the heat resistance of the above developed titanium diboride-based refractory materials is not always sufficient due to the use of a nickel-phosphorus alloy with a relatively low melting point down to 890.degree. C.
Another problem of the metal diboride-based sintered bodies for refractory and abrasive uses is that they are prepared by sintering at an undesirably high sintering temperature of 1800.degree. C. or higher.